Roast-flotation process for upgrading molybdenite flotation concentrates

ABSTRACT

A molybdenite flotation concentrate, usually a copper sulfide concentrate containing considerable molybdenite as well as other sulfides, such as pyrite, and a relatively small amount of siliceous gangue, is upgraded by, first, adding thereto inert, particulate solid, diluent material that can be easily removed subsequent to roast-conditioning treatment of the concentrate, for example, relatively coarse sand, finely ground mica, or crushed or ground limestone, in sufficient quantity to permit abnormally high roasting temperatures without igniting the charge; then, by roasting the resulting mixture at an abnormally high temperature, usually a temperature that, but for the presence of the diluent material, would ignite the charge and oxidize the molybdenite; and, finally, by treating the roasted concentrate by flotation for recovering the molybdenite as an upgraded molybdenite concentrate. Although the molybdenite is upgraded by flotation treatment of the roasted concentrate in conventional manner, such flotation treatment is facilitated by the higher than normal temperature to which the material has been subjected during the roasting step. The diluent material is removed by appropriate separation steps applied either to the roasted product before flotation of some subsequent stage.

United States Patent Last et a1.

[ Mar. 18, 1975 CONCENTRATES [75] Inventors: Arthur W. Last, Salt Lake City;

George L. Fraser, Magna, both of Utah [73] Assignee: Kennecott Copper Corporation,

New York, NY.

[22] Filed: Jan. 2, 1973 [21] Appl. No.: 320,167

[52] US. Cl 75/2, 75/7, 75/20 R, 432/27 [51] int. Cl. B03d 1/08 [58] Field of Search 75/2, 36, 37, 6, 7, 20 R; 432/27; 423/659 [56] References Cited UNITED STATES PATENTS 1,492,818 5/1924 Thornhill 75/37 1,801,105 4/1931 Phelan et al..... 75/2 X 1,865,153 6/1932 Taplin 75/2 X 2.674612 4/1954 Murphree 75/26 X 3,427.148 2/1969 Peters ct al 75/37 X 3,585,023 6/1971 Vlnaty et al. 75/36 X 3.630.501 12/1971 Shabaker 432/27 X FOREIGN PATENTS OR APPLICATIONS 454,695 2/1949 Canada 75/2 MOLYBENITE ROUGPg FLOTATION CONCENTRATE Primary Examiner-Allen E. Curtis Assistant Ex'aminer--Thomas A. Waltz Attorney, Agent, or Firm-Mallinckrodt & Mallinckrodt [57] ABSTRACT v A molybdenite flotation concentrate, usually a copper sulfide concentrate containing considerable molybdenite as well as other sulfides, such as pyrite, and a relatively small amount of siliceous gangue, is upgraded by, first, adding thereto inert, particulate solid, diluent material that can be easily removed subsequent to roast-conditioning treatment of the concentrate, for example, relatively coarse sand, finely ground mica, or crushed or ground limestone, in sufficient quantity to permit abnormally high roasting temperatures without igniting the charge; then, by roasting the resulting mixture at an abnormally high temperature, usually a temperature that, but for the presence of the diluent material', would ignite the charge and oxidize the molybdenite; and, finally, by treating the roasted concentrate by flotation for recovering the molybdenite as an upgraded molybdenite concentrate. Although the molybdenite is upgraded by flotation treatment of the roasted concentrate in conventional manner, such flotation treatment is facilitated by the higher than normal temperature to which the material has been subjected during the roasting step. The diluent material is removed by appropriate separation steps applied either to the roasted product before flotation of some subsequent stage.

11 Claims, 1 Drawing Figure OARSE QUARTZ SAND A5 C0 ER LFlDE l C 5-|5% AV tJ ElGHT M08 SILICEOUS GANGUE) INERT PARTlCLLATE SOLID DILUENT PHY AL TURE M YBDEN E OONCENT TE OUAR SA N D DlLLi NT FROTHER REAGENT GANGUE FLOTAT ION TD SMELTER FLOTATXON ROASTER (0.9. 550E T0 750"?) I SCREENlNG COLLECTOR REAGENT FOR MOLYBDENITE M05 FLOAT UPGRADED MOLYBDENITE I PATENIEDIIARIBIQYEI A 3.871.867

MOLYBDENITE ROUGHER FLOTATION CONCENTRATE COPPER SULFIDES PYRITE COARSE QUARTZ SAND AS 5I5% Y WEIGHT M08 SILICEOUS GANGUE) INERT PARTICULATE SOLID, DILUENT MIXER PHYSICAL MIXTURE E CONCENTRATE AND QUARTZ SAND DILUENT ROASTER (8.9. 550E TO 750FI FROTHER SCREENING REAGENT FLOAT SINK GANGUE WASTE v SULFIDE CONCENTRATE COLLECTOR REAGENT FOR MOLYBDENITE FLOTATION I COPPER SULFIDES, PYRITE etc. M082 FLOAT W UPGRADED MOLYBDENITE ROAST-FLOTATION PROCESS FOR UPGRADING MOLYBDENITE FLOTATION CONCENTRATES BACKGROUND OF THE INVENTION Field:

The invention is in the narrow but important field of upgrading flotation concentrates containing considerable quantities of molybdenite.

State of the Art:

Many copper sulfide ores contain relatively small amount of molybdenite (M05 Both the copper sulfide minerals and the molybdenite are conventionally concentrated in common by floatation, resulting in a general flotation concentrate containing varying amounts of molybdenite, depending upon the ore and the number of cleaning steps utilized. Such copper sulfide concentrate usually also contains pyrite and some gangue materials, and is normally further treated to produce a molybdenite flotation concentrate in which either copper sulfides or molybdenite predominates. A common procedure for separating the molybdenite from the copper sulfides, pyrite, and gangue materials remaining in such molybdenite flotation concentrate is to filter the concentrate and deactivate the copper sulfides, pyrite, and gangue materials therein by roasting. The roasted concentrate is then repulped and subjected to flotation for upgrading the molybdenite content.

The effectiveness of the procedure, or similar roasting procedure applied to other types of molybdenite I concentrates, is dependent upon the temperature at which the roaster is maintained. If the temperature is too low, the copper sulfide minerals, pyrite, and gangue materials are not deactivated and, in a subsequent flotation step for the recovery of molybdenite as a froth product, will report in the froth along with the molybdenite. If the temperature is too high, the copper sulfide minerals and pyrite will ignite and cause a rapid rise in temperature which will oxidize the molybdenite and thereby prevent effective upgrading of the molybdenite values by subsequent flotation, Since it is very difficult to maintain the roasting temperature at an optimum (just below 600F) for the desired deactivation, the common practice is to operate at a temperature below the optimum (e.g. between 450F and 550F) rather than to risk ignition of the charge in the roaster.

This results in a lower concentration of molybedenite 1 in the subsequent flotation froth product.

Objectives:

It was an objective in the making of this invention to provide for roasting the molybdenite flotation concentrate concerned at abnormally high temperatures, i.e., at temperatures above the normal upper limit of 550F and often above 600F (which is usually high enough to cause the charge to ignite), so as to improve recov- -ery of the molybdenite by subsequent flotation.

SUMMARY OF THE INVENTION In accordance with the invention, a molybdenite concentrate is mixed with a sufficient quantity of an inert, particulate solid, diluent material to enable roasting at an abnormally high temperature, i.e., above 550F. The diluent material must be of a type easily recoverable at some convenient time following roasting of the mixture. Quartz sand of coarse grain size relative to the finely ground solids in an ore pulp, crushed or ground limestone, and finely ground micaceous material are ideal diluent materials. The mixture of diluent material and molybdenite concentrate is usually subjected to roasting in a furnace, such as a multiple hearth roaster, at a temperature in the neighborhood of-600F. or above as high as 760 having been successfully employed) for a time sufficient to deactivate the copper and other sulfide minerals, substantially without igniting such minerals or converting the molybdenite in the concentrate to a molybdenum oxide.

Following the roasting step, the molybdenite is upgraded by flotation and the inert diluent material is separated for reuse in the process. The manner of removing the diluent material will depend upon its nature and whether it follows the molybdenite or remains with the residue. For example, if it is coarse sand or the like, it is removed by screening of the roasted concentrate prior to flotation; if it is finely ground micaceous material, it is removed by flotation of the roasted mixture, using only a frother as a reagent; if it is crushed or ground limestone, it is removed by leaching the roasted mixture after separation of the'molybdenite therefrom.

THE DRAWING DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT As shown in the accompanying flowsheet, the molybdenite concentrate subjected to upgrading procedures in accordance with the invention is normally a copper sulfide flotation concentrate containing considerable quantity of molybdenite. The quantity may vary from 5 percent by weight to as high as percent, depending upon the mining property from which the original ore was obtained and the milling procedures applied to it. In the particular procedure illustrated, the molybdenite concentrate contains from 5 to 15 percent by weight M08 Such molybedenite flotation concentrate is intimately mixed with an inert, particulate solid, diluent material, which, in this instance, is a coarse quartz sand having a grain size larger than the size of the particles of ore in the concentrate. The quantity of the diluent material necessary to achieve the purposes of the invention will vary in accordance with the particular feed material, etc., but should be at least enough to be effective in preventing ignition of the charge and oxidation of the molybdenite therein when the abnormally high roasting temperatures (i.e., above 550F.) are employed in accordance with the invention. As previously indicated, other diluent materials, such as mica or crushed limestone, can be employed either alone or in combination, but the diluent must be inert to the reaction in the roaster and physically recoverable from the roasted concentrate. Part of the diluent may be naturally present in the ore material itself as gangue.

The resulting mixture of molybdenite concentrate and diluent material is subjected to roasting in a suitable furnace, such as a multiple hearth roaster, to deactivate the copper, iron, and various sulfides other than molydbenite, without altering the surfaces of the particles of molybdenite. Whereas temperatures of at most between 550F. and 600F. have heretofore been attainable without ignition of the copper and iron sulfides, though in commercial practice temperatures above 550F. are not normally employed, the mixture containing the diluent material can be heated to usual ignition temperatures of 600F. and above, without danger of igniting the furnace charge. For example, temperatures of 650F. to 750F. and above are possible without igniting the charge or converting the molybdenite to molybdenum oxides. Such high temperatures provide for almost complete alteration of the surfaces of sulfide minerals other than molybdenite, and, therefore, permit more selective separation of the molybdenite from such sulfide minerals in subsequent separation steps. In addition, the higher temperatures ensure complete removal of flotation reagents, and enhance the floatability of micaceous gangue materials in subsequent flotation steps.

The period of time necessary to deactivate minerals in the roaster will vary with the concentration of such minerals, the roasting temperature, and the amount of diluent material in the mixture.

After the mixture has been roasted, it is screened to separate the coarse grained quartz sand diluent from the relatively fine ore particles. Such diluent can then be recycled for continued use in the process. The remaining roasted molybdenite concentrate is subjected to conventional gangue flotation with a frother reagent, such as an alcohol, to float the gangue materials, including any micaceous gangue that might be naturally present as a further diluent, leaving the mineral sulfides as a sink product.

If finely ground mica or micaceous material is employed as the added diluent, it is separated from the roasted concentrate by means of the aforementioned gangue flotation procedure, the screening stage being eliminated.

An upgraded molybdenite final product results from subjecting the sulfide concentrate obtained from gangue flotation to the usual flotation treatment with a collector reagent, such as burner oil, for recovering molybdenite in the froth.

Crushed or ground limestone as the diluent can be effectively eliminated from the sulfide tailings obtained from the floatation step applied to the sulfide concentrate by leaching such tailings with hydrochloric acid.

1 If found economical, the dissolved lime can be precipitated from the acid leach solution by known procedures for recycling. The following laboratory tests demonstrate the effectiveness of the process.

EXAMPLE I A 200 gram sample of molybdenite flotation concentrate was mixed with 800 grams of -+30 mesh Ottawa (quartz) sand. The mixture was then heat-treated in an open pan in a laboratory muffle furnace with rabbling. The charge was heated to a temperature of 700F. and held at temperatures between 700F. and 750F. for minutes. The charge was then cooled, the Ottawa sand removed by screening, and the recovered, heat-treated sample subjected to flotation for the removal of micaceous gangue by flotation with an alcohol frother, followed by flotation of molybdenite with burner oil as the collector. The following flotation metallurgy was achieved.

/r Distri- Product Weight 7r M05 bution-M05 Gangue Concentrate l4.37 3.04 5.79 Tailing 75.31 1.12 ll.l8 M05 Concentrate 10.32 60.7 83.03 Calculated Feed 100.00 7.5 100.00

EXAMPLE II This test was conducted in substantially the identical manner as that of Example I, except that the temperature during the 30 minute heat-treatment was maintained between 600F. and 630F. The following flotation metallurgy was achieved:

7: Distri- Product 71 Weight MoS bution M05 Gangue Concentrate I485 097 L79 Tailing 73.32 0.98 8.93 M08 Concentrate l 1.83 60.7 89.28 Calculated Feed 100.00 8.0 100.00

EXAMPLE III Distri- Product /1 Weight 7( M05 bution M05 Gangue Concentrate l8.48 l4,2 29.98 Tailing 73.39 2.77 23.22 M08 Concentrate 8.13 50.4 46.80 Calculated Feed l00.00 100.00

Example ll established that, in the heat-treatment step, the temperature could be maintained between 600F. and 630F. without developing ignition and burning ofthe sample In subsequent flotation, 89.3 percent of the molybdenite was recovered as a froth concentrate, nearly twice the recovery effected in Example lll in which lack of effective control pursuant to the invention resulted in ignition of the charge.

Example 1 established that high temperatures of 700F. to 750F. could be reached in the heattreatment step with, at the most, minor adverse effects upon subsequent flotation processing.

In Example lll, the temperature limit to which a particular mixed molybdenite-chalcopyrite-pyritesiliceous gangue mixture could be heated in an open air atmosphere was shown. In this instance, ignition was observed at 600F., temperatures increased rapidly because of burning" of the charge. In subsequent flotation, only 46.8 percent of the molybdenite could be recovered as a froth concentrate.

Laboratory tests have shown that the grade of a molybdenite concentrate to which the process of the invention has been applied is increased approximately percent over what it would have been if the material had been roasted at the usual safe temperature.

Whereas the invention is here illustrated and described in terms of specific details of the best mode presently contemplated for carrying it out in practice, it is to be understood that many changes can be made without departing from the inventive concepts here taught and set forth in the following claims.

We claim:

1. In a molybdenite recovery process applicable to a finely divided ore material containing molybdenite and sulfide minerals other than molybdenite, but relatively little gangue, which ore material has been previously treated by flotation and which process comprises roasting said ore material to deactivate sulfide minerals other than molybdenite and subjecting the roast product to flotation for the recovery of the molybdenite as a froth concentrate, the improvement which comprises mixing with said ore material under substantially ambient conditions a sufficient quantity of a particulate, solid diluent to prevent ignition of the roast at a temperature at which ignition would otherwise occur, said diluent being chemically inert with respect to the molybdenite and sulfide materials in said ore material; roasting the mixture of ore material and diluent at a temperature at which ignition would occur if said diluent were not present; and separating the diluent from the roasted ore material.

2. A process in accordance with claim 1, wherein the diluent is removed from the roast product before said product is subjected to flotation.

3. A process in accordance with claim diluent is removed from the roast product by a flotation stage in the flotation of said product.

4. A process in accordance with claim 1, wherein the diluent is removed from the roast product subsequent to the flotation thereof.

5. A process in accordance with claim 1, wherein the diluent is selected from one or more of the group consisting of quartz sand, micaceous material, and limestone.

6. A process in accordance with claim 5, wherein the diluent comprises quartz sand of relatively coarse particle sizefwhich is removed from the roast product by screening said material prior to flotation.

7. A process in accordance with claim 5, wherein the diluent comprises micaceous material which is re,- moved from the roast product in a gangue flotation stage utilizing only a frother reagent.

8. A process in accordance with claim 5, wherein the diluent comprises limestone which is removed from the roast product by chemical leaching of a flotation product containing same.

9. A process in accordance with claim 1, wherein the roasting temperature is within a range of from 550 to 760F.

10. A process in accordance with claim 1, wherein a portion of the total diluent content of the ore material and diluent mixture effective for the purpose specified is naturally present in the ore material itself.

11. A process in accordance with claim 1, wherein the ore material includes copper, sulfides, iron sulfides,

and a relatively small amount of siliceous gangue.

* l l l l, whereinthe' 

1. IN A MOLYBDENITE RECOVERY PROCESS APPLICABLE TO A FINELY DIVIDED ORE MATERIAL CONTANING BOLYBDENITE AND SULFIDE MINERALS OTHER THAN MOLYBDENITE, BUT RELATIVELY LITTLE GANGUE, WHICH ORE MATERIAL HAS BEEN PREVIOUSLY TREATED BY FLOATATION AND WHICH PROCESS COMPRISES ROASTING SAND ORE MATERIAL TO DEACTIVATE SULFIDE MINERALS OTHER THAN MOLYBDENITE AND SUBJECTING THE ROAST PRODUCT TO FLOTATION FOR THE RECOVERY OF THE MOLYBDENITE AS A FROTH CONCENTRATE, THE IMPROVEMENT WHICH COMPRISES MIXING WITH SAID ORE MATERIAL UNDER SUBSTANTIALLY AMBIENT CONDITIONS A SUFFICIENT QUANTITY OF A PARTICULATE, SOLID DILUENT TO PREVENT IGNITION OF THE ROAST AT A TEMPERATURE AT WHICH IGNITION WOULD OTHERWISE OCCUR, SAID DILUENT BEING CHEMICALY INERT WITH RESPECT TO THE MOLYBDENITE AND SULFIDE MATERIALS IN SAID ORE MATERIAL; ROASTING THE MIXTURE OR ORE MATERIAL AND DILUENT AT A TEMPERATURE AT WHICH IGNITION WOULD OCCUR IF SAID DILUENT WERE NOT PRESENT; AND SEPARATING THE DILUENT FROM THE ROASTED ORE MATERIAL.
 2. A process in accordance with claim 1, wherein the diluent is removed from the roast product before said product is subjected to flotation.
 3. A process in accordance with claim 1, wherein the diluent is removed from the roast product by a flotation stage in the flotation of said product.
 4. A process in accordance with claim 1, wherein the diluent is removed from the roast product subsequent to the flotation thereof.
 5. A process in accordance with claim 1, wherein the diluent is selected from one or more of the group consisting of quartz sand, micaceous material, and limestone.
 6. A process in accordance with claim 5, wherein the diluent comprises quartz sand of relatively coarse particle size, which is removed from the roast product by screening said material prior to flotation.
 7. A process in accordance with claim 5, wherein the diluent comprises micaceous material which is removed from the roast product in a gangue flotation stage utilizing only a frother reagent.
 8. A process in accordance with claim 5, wherein the diluent comprises limestone which is removed from the roast product by chemical leaching of a flotation product containing same.
 9. A process in accordance with claim 1, wherein the roasting temperature is within a range of from 550* to 760*F.
 10. A process in accordance with claim 1, wherein a portion of the total diluent content of the ore material and diluent mixture effective for the purpose specified is naturally present in the ore material itself.
 11. A process in accordance with claim 1, wherein the ore material includes copper, sulfides, iron sulfides, and a relatively small amount of siliceous gangue. 